Image reader

ABSTRACT

A CCD camera  10  picks up multiple adjacent targeted portions on a document  2 , and to obtain distance information, a distance measurement unit  11  calculates the distances to the targeted portions of the document  2 . Based on the distance information, a synthesization controller  16  prepares perspective information for the images, adjusts the sizes of the multiple obtained plane images so they correspond, and synthesizes the resultant plane images to form a single image.

This is a Division of application Ser. No. 09/717,155 filed Nov. 22,2000 now U.S. Pat. No. 7,016,551. The entire disclosure of the priorapplication is hereby incorporated by reference herein in its entirety.

BACKGROUND

The present invention relates to an image reader that is appropriate fora TV telephone or a TV conference system, and relates in particular toan image reader that can be compactly and lightly constructed, and thatcan accurately and quickly read the image of even a distorted object.

An example, conventional image reader is disclosed in JP-A-11-136564.

This image reader comprises: an image pickup unit, for obtaining, usingan image forming optical system having a variable magnification rate, animage of an object document at a predetermined magnification rate; adistance sensor, for measuring distances to three targeted points on theobject document; and an image synthesizer, for employing, when the imagepickup unit sequentially acquires the images of adjacent targetedportions at the same magnification rate, the distance values obtained bythe distance sensor to transform multiple, thus obtained images intothose equivalent to images viewed from the front, and for synthesizingthe transformed images to prepare a single image of the entire document.According to this image reader, the document can be read veryaccurately, even when the document is positioned so that it is tilted.Further, since glass platen that is equal to or larger than a documentis not required, the size of the image reader can be reduced.

However, since a premise of the employment of a conventional imagereader is that a document have a flat face, such an image reader can notsatisfactorily read a document that is bent, and distorted documentinformation is obtained. When, for example, a page of an opened book isto be read, the images, such as character images, at the bound portion,where the page is bent, can not be read accurately.

When a document that is tilted is to be read, the distance to the imagepickup unit varies, depending on the portion of the document that is tobe read. Thus, the sizes of the individual images differ, and thesynthesized image is distorted. In this case, the magnification rate canbe changed by referring to the characteristics of adjacent images forthe performance of the synthesization process. However, according tothis method, the magnification rate must be changed repeatedly, and anextended time is required for the synthesization process.

SUMMARY OF THE INVENTION

It is, therefore, one objective of the present invention to provide animage reader that can accurately and quickly read an object, even onethat is distorted.

It is another objective of the present invention to provide an imagereader that can be compactly and lightly constructed.

To achieve the above objectives, according to the present invention, animage reader comprises:

image pickup means, for obtaining multiple targeted adjacent portions atthe same optical magnification rate, and for obtaining multiple images;

measurement means, for measuring multiple distances to multiplerespective points that are selected on the targeted portions; and

processing means, for employing the multiple distances to performperspective transformations of the multiple images to acquire multipleplane images, and for altering the sizes of the multiple plane images sothat all sizes correspond.

With this configuration, the perspective transformation is performed forthe images obtained for the plane images, so that even a distortedobject can be accurately read. Further, since a plurality of planeimages are altered to provide corresponding sizes, the imagesynthesization process can be performed quickly.

Further, to achieve the above objectives, an image reader comprises:

image pickup means, for acquiring an image of an object;

measurement means, for measuring multiple distances to multiplerespective points that are selected on the object; and

processing means, for employing the multiple distances to performperspective transformations for the image to obtain a plane image.

With this arrangement, multiple images can be acquired using a hand-heldimage reader, distances to multiple target portions can be measured, anda small and light apparatus can be manufactured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram showing an image reading system to which an imagereader according to a first embodiment of the present invention isapplied.

FIG. 1B is a block diagram illustrating the control system of the imagereader according to the first embodiment.

FIG. 2 is a diagram showing perspective transformation and magnificationrate calculations performed by the synthesization controller in theimage reader according to the first embodiment.

FIG. 3 is a diagram showing the synthesization processing performed bythe synthesization controller of the image reader according to the firstembodiment.

FIG. 4 is a flowchart showing the processing performed by the imagereader according to the first embodiment.

FIG. 5 is a block diagram showing the control system of an image readeraccording to a second embodiment of the present invention.

FIG. 6 is a block diagram showing the control system of an image readeraccording to a third embodiment of the present invention.

FIG. 7A is a diagram showing an image reading system to which an imagereader according to a fourth embodiment of the present invention isapplied.

FIG. 7B is a block diagram illustrating the control system of the imagereader according to the fourth embodiment.

FIG. 8 is a diagram showing perspective transformation and magnificationrate calculations performed by the synthesization controller in theimage reader according to the fourth embodiment.

FIG. 9 is a diagram showing the synthesization processing performed bythe synthesization controller of the image reader according to thefourth embodiment.

FIG. 10A is a diagram showing a complete image for the synthesizationprocess performed by the synthesization controller of an image readeraccording to a fourth embodiment.

FIG. 10B is a diagram showing the processing performed to extract afeature for the synthesization process.

FIG. 11A is a diagram showing a text area for the synthesizationprocess.

FIG. 11B is a diagram showing another text.

FIG. 11C is a diagram showing the synthesization of image segments.

FIG. 12A is a diagram showing the superimposition process performed bythe synthesization controller of the image reader according to thefourth embodiment.

FIG. 12B is an enlarged diagram showing the synthesized portion.

FIG. 13 is a flowchart showing the processing performed by the imagereader according to the fourth embodiment.

FIG. 14 is a block diagram showing the control system of an image readeraccording to a fifth embodiment of the present invention.

FIG. 15 is a block diagram showing the control system of an image readeraccording to a sixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

First Embodiment

FIG. 1A is a diagram showing an image reading system that employs animage reader according to a first embodiment of the present invention.The image reading system comprises: an image reader 1, for reading adocument 2, an object; and a computer 4, which is connected to the imagereader 1 by an interface 3, such as an image signal line 3A and anRS232C cable 3B. The image reader 1 includes a main body 1A in which adigital CCD camera, which will be described later, is mounted, and ascanning unit 12, for pivoting the main body 1A along an axis 12 a andat a shaft 12 b in a direction α or β, as is indicated by an arrow.

The computer 4 includes a computer main body 40 in which a CPU and amemory are mounted; a display unit 41, such as a CRT; and an input unit42, such as a keyboard or a mouse. The computer 4 processes an imagethat is read, or controls the zooming and the focusing of the digitalCCD camera and the positioning that is required to read an image. Thecomputer main body 40 also includes a drive 40 a for reading data from amemory card, such as a floppy disk, that has been loaded.

FIG. 1B is a diagram showing the control system of the image reader 1.The main body 1A of the image reader 1 comprises: a digital CCD camera,having a zooming function and a focusing function; a distancemeasurement unit 11, for obtaining two-dimensional distance information(distances to n×m measurement points) for the targeted portions of adocument 2 that is acquired by the CCD camera 10; a scanner 13, forchanging the viewing directions of the CCD camera 10 and the distancemeasurement unit 11; a controller 13, for controlling the CCD camera 10,the distance measurement unit 11 and the scanner 12; a signal processor14, for performing signal processing, such as amplification orcorrection, for a pickup signal received from the CCD camera 10; animage memory 15, for storing images; and a synthesis controller 16 forsynthesizing multiple images stored in the image memory 15.

The distance measurement unit 11 employs the pattern projection methodor the phase distribution measurement method to obtain two-dimensionalinformation for the distance to the document 2. According to an examplepattern projection method, whereby a laser beam is employed to generate,based on pattern code, a light pattern that consists of multiple regionsthe intensity of which is modulated to obtain triple level or higherdata, the light pattern produces an image of the document 2 and thelight reflected from the document 2 is acquired to prepare an imagepattern, whereafter, the pattern code and the pattern image are employedto obtain information for measuring the distance to the document 2.Using this method, since the laser beam used as a light source has alinearity that little affects the depth of focus, the edges between theregions are not blurred, and for the depth, the measurable range isexpanded. Further, since an image of the document 2 is projected by thepattern light at the modulated intensity, two-dimensional informationfor measuring the distance to the document 2 can be obtained using asingle image pickup. In addition, there is an example phase distributionmeasurement method whereby light, whose intensity is modulated at apredetermined frequency, is emitted and strikes the document 2, andwhereby a composite light, consisting of light reflected by the document2 and the above emitted light, is received by a plane sensor that isconstituted by multiple, two-dimensionally arranged pixels, andinformation for the distance to the document 2 is obtained based on thedetection signal. According to this method, the two-dimensionalinformation for the distance to the document 2 can be obtained by asingle one measurement.

The synthesization controller 16 performs perspective transformation,calculation of a magnification rate, the alteration of image size andimage synthesization based on an image signal fetched into the imagememory 15 and the information obtained by the distance measurement unit11 for the distance between the document and the CCD camera 10.

FIG. 2 is a diagram for the perspective transformation and calculationof a magnification rate that are performed by the synthesizationcontroller 16. In FIG. 2, black dots represent the points used for themeasurement of distances. The synthesization controller 16 employs thedistance information (L₁, L₂, L₃ and L₄) to estimate similar curves, andto identify the shape of an object. Then, the synthesization controller16 performs a perspective transformation so that an image 21 stands,upright relative to a pickup device 10 a of the CCD camera 10, andconstitutes a plane. In FIG. 2, the distances L₁, L₂, L₃ and L₄ from thepickup device 10 to the individual points of the image 21 aretransformed into distances L′₁, L′₂, L′₃ and L′₄, and the image obtainedby the perspective transformation is called a “plane image” 22.Furthermore, the synthesization controller 16 calculates multipledistances on the plane image 22, e.g., distances between points A′ andB′ and between points A′ and C′, and performs a “magnification ratecalculation” to obtain a magnification rate relative to a predeterminedreference size.

FIG. 3 is a diagram showing an image synthesization process performed bythe synthesization controller 16. Assuming that multiple images areobtained so that adjacent images 23 include overlapping size Δx and Δyareas 24, the synthesization controller 16 aligns the sizes of the planeimages 22. Then, the synthesization controller 16 determines thelocations whereat the density patterns of the overlapping areas 24 ofthe plane images 22 to be synthesized are the most similar to thedensity patterns of the adjacent images 23 that are already stored inthe image memory 15. The images 23, excluding the overlapping areas 24,are then fitted into the locations. Through this “synthesizationprocess”, one complete image 20 is finally completed.

FIG. 4 is a flowchart showing the processing performed by the imagereading system. First, a user manipulates an input unit 42 of thecomputer 4 to enter information required for the reading of the document2, such as the range for reading the document 2 and a desiredresolution. The CPU of the computer 4 employs the information entered bythe input unit 42 to determine the number of images to be acquired, andtransmits via the RS232C cable 3B a control signal for the CCD camera 10and the scanner 12 to the controller 13 of the image reader 1. Then,based on the control signal received from the computer 4, the controller13 controls the zooming and focusing functions of the CCD camera 10 andthe scanner 12 and initiates the reading of the document 2. At thistime, as was previously described, the CCD camera 10 acquires theindividual portions of the document 2 at the same optical magnificationrate, so that adjacent images include overlapping areas, and transmitsan image signal to the signal processor 14. The signal processor 14 thenperforms signal processing, such as an amplification process and variouscorrection processes, for the image signal received from the CCD camera10, and stores the resultant image signal in the image memory 15. At thesame time as the CCD camera begins the acquisition of the image pickup,the distance measurement unit 11 obtains two-dimensional measurementinformation for the distance to the target portion of the document 2,which is acquired by the CCD camera 10, and transmits the distanceinformation via the controller 13 to the synthesization controller 16(ST1).

Subsequently, based on the distance information obtained by the distancemeasurement unit 11 (ST2), the synthesization controller 16 analyzes theshape of the targeted portion of the document 2 and performs aperspective transformation for the image that is read (ST3). Thereafter,the image acquisition (ST1), the shape analysis of the target portion ofthe document 2 (ST2) and the perspective transformation of the image(ST3) are sequentially performed. When the synthesization controller 16has performed the perspective transformation for all the images, itemploys the obtained distance information to calculate the magnificationrate for each plane image (ST4). The synthesization controller 16compares the image sizes (magnification rates) of the plane images, andchanges to the maximum or to the minimum the sizes of the plane images(ST5) Following this, the synthesization controller 16 compares eachplane image with its adjacent image (ST6), corrects for distortions(ST7), synthesizes the plane images to form a single complete image, andstores the obtained image in the image memory 15 (ST8). The imagereading is thereafter completed, and via the image signal line 3A, thecomplete image stored in the image memory 15 is transmitted to thecomputer 4 by the controller 13 and is displayed by the display unit 41.

According to the first embodiment, since the image that is acquired istransformed into a plane image, even that portion of an image near thebound portion of an opened book, or on the curved face of a can, can beaccurately read. Furthermore, since the image synthesization isperformed after the image sizes of the plane images have been aligned,the time required for synthesization can be reduced.

In the first embodiment, image synthesization is performed by the mainbody 1A. However, images and the information required for synthesizationmay be transferred as needed via the interface 3 to the computer 4,which may then perform image synthesization.

Second Embodiment

FIG. 5 is a diagram showing an image reader according to a secondembodiment. In the second embodiment, the scanner 12 in the firstembodiment is not employed, and a detachable memory card 17, such as aflash memory or a RAM card, is mounted in a main body 1A to provide aportable image reader.

The processing for the second embodiment will now be described. First, auser sets a resolution using a zooming function, and reads images usinga hand-held image reader, so that the images have a specific overlappingarea. At this time, together with the images, the distance informationis also obtained. As in the first embodiment, multiple images aresynthesized to form one complete image, and the complete image is readfrom the image memory 15 and written to the memory card 17. The userloads the memory card 17 into a driver 40 a of a computer 4, where atthe complete image is read, and thereafter the image is displayed on adisplay unit 41.

According to the second embodiment, since a scanner 12 is not included,and since the synthesization of plane images may be performed by thecomputer 4, instead of by an image reader 1, a compact and light imagereader can be constructed that is easily carried and transported.

Third Embodiment

FIG. 6 is a diagram showing an image reader according to a thirdembodiment. In the third embodiment, all the images and distanceinformation are written on a memory card 17, and a computer 4 thereaftersynthesizes images. According to the this embodiment, a more compact andlighter image reader can be obtained that is more suitable for carrying.

Fourth Embodiment

FIG. 7A is a diagram showing an image reading system that employs animage reader according to a fourth embodiment of the present invention.The image reading system comprises: an image reader 101, for reading adocument 102, an object; and a computer 104, which is connected to theimage reader 101 by an interface 103, such as an image signal line 103Aand an RS232C cable 103B. The image reader 101 includes a main body 101Ain which a digital CCD camera, which will be described later, ismounted, and a scanning unit 112, for pivoting the main body 101A alongan axis 112 a and at a shaft 112 b in a direction α or β, as isindicated by an arrow.

The computer 104 includes a computer main body 140 in which a CPU and amemory are mounted; a display unit 141, such as a CRT; and an input unit142, such as a keyboard or a mouse. The computer 4 processes an imagethat is read, or controls the zooming and the focusing of the digitalCCD camera and the positioning that is required to read an image. Thecomputer main body 140 also includes a drive 140 a for reading data froma memory card, such as a floppy disk, that has been loaded.

FIG. 7B is a diagram showing the control system of the image reader 101.The main body 101A of the image reader 101 comprises: a digital CCDcamera, having a zooming function and a focusing function; a distancemeasurement unit 111, for obtaining two-dimensional distance information(distances to n×m measurement points) for the targeted portions of adocument 102 that is acquired by the CCD camera 110; a scanner 113, forchanging the viewing directions of the CCD camera 110 and the distancemeasurement unit 111; a controller 113, for controlling the CCD camera110, the distance measurement unit 111 and the scanner 112; a signalprocessor 114, for performing signal processing, such as amplificationor correction, for a pickup signal received from the CCD camera 110; animage memory 115, for storing images; and a synthesis controller 116 forsynthesizing images stored in the image memory 115.

The distance measurement unit 111 employs the pattern projection methodor the phase distribution measurement method to obtain two-dimensionalinformation for the distance to the document 102. According to anexample pattern projection method, whereby a laser beam is employed togenerate, based on pattern code, a light pattern that consists ofmultiple regions the intensity of which is modulated to obtain triplelevel or higher data, the light pattern produces an image of thedocument 102 and the light reflected from the document 102 is acquiredto prepare an image pattern, whereafter, the pattern code and thepattern image are employed to obtain information for measuring thedistance to the document 102. Using this method, since the laser beamused as a light source has a linearity that little affects the depth offocus, the edges between the regions are not blurred, and for the depth,the measurable range is expanded. Further, since an image of thedocument 102 is projected by the pattern light at the modulatedintensity, two-dimensional information for measuring the distance to thedocument 102 can be obtained using a single image pickup. In addition,there is an example phase distribution measurement method whereby light,whose intensity is modulated at a predetermined frequency, is emittedand strikes the document 102, and whereby a composite light, consistingof light reflected by the document 102 and the above emitted light, isreceived by a plane sensor that is constituted by multiple,two-dimensionally arranged pixels, and information for the distance tothe document 102 is obtained based on the detection signal. According tothis method, the two-dimensional information for the distance to thedocument 102 can be obtained by a single one measurement.

Based on an image signal fetched into the image memory 115 and theinformation obtained by the distance measurement unit 111 for thedistance between the document and the CCD camera 110, the synthesizationcontroller 116 performs perspective transformation, calculation of amagnification rate, the alteration of image size, and a process forsynthesizing image segments that are acquired by superimposing aspecific area of the document 102 to a preview image obtained for theoverall document 102.

FIG. 8 is a diagram for the perspective transformation and calculationof a magnification rate that are performed by the synthesizationcontroller 116. In FIG. 8, black dots represent the points used for themeasurement of distances. The synthesization controller 116 employs thedistance information (L₁, L₂, L₃ and L₄) to estimate similar curves, andto identify the shape of an object. Then, the synthesization controller116 performs a perspective transformation so that a preview image 119 ora image segment 121 stands, upright relative to a pickup device 110 a ofthe CCD camera 110, and constitutes a plane. In FIG. 8, the distancesL₁, L₂, L₃ and L₄ from the pickup device 110 to the individual points ofthe image 119 or 121 are transformed into distances L′₁, L′₂, L′₃ andL′₄, and the preview image 119 or the image segment 121 obtained by theperspective transformation is called a “plane preview image” 120 or a“plane image” 122. Furthermore, the synthesization controller 116calculates multiple distances on the plane preview image 120 or theplane image 122, e.g., distances between points A′ and B′ and betweenpoints A′ and C′, and performs a “magnification rate calculation” toobtain a magnification rate relative to a predetermined reference size.

FIG. 9 is a diagram showing the synthesization process performed by thesynthesization controller 116. The synthesization controller 16 reducesthe size of the plane image segment 122 to na/np (na: the opticalmagnification rate when the complete image was acquired; and np: theoptical magnification rate when the image segment was acquired) toobtain a plane image segment 123. Then, the synthesization controller116 determines the location whereat the density pattern of theperipheral area of the plane image segment 23 most closely resembles thedensity pattern of the plane preview image 120, which is stored in theimage memory 115, and that corresponds to the complete document 102. Thesynthesization controller 16 then fits the image segment 123 into thatlocation, and completes the “synthesization process”. It should be notedthat, during this synthesization process, a corresponding area in theplane preview image 120 is deleted, and the plane image segment 123 isfitted into that area.

FIGS. 10 to 13 are diagrams and a flowchart showing the processingperformed by the image reading system. First, a user manipulates aninput unit 142 of the computer 104 to enter information required for thereading of the document 102, such as the range for the reading of thedocument 102 and a desired resolution. Based on the information enteredby the input unit 142, the CPU of the computer 104 transmits, via theRS232C cable 103B, a control signal for the CCD camera 110 and thescanner 112 to the controller 113 of the image reader 101. Based on thecontrol signal received from the computer 104, the controller 113controls the zooming and focusing functions of the CCD camera 110 andthe scanner 112 and initiates the reading of the document 102. The CCDcamera 110 acquires a complete image of the document 102, and transmitsto the signal processor 114 a pickup signal for the preview image 119.The signal processor 114 performs signal processing, such as anamplification process and various correction processes, for the imagesignal received from the CCD camera 110, and stores the resultant imagesignal in the image memory 115. At the same time as the CCD camerabegins to acquire the image, the distance measurement unit 111 obtains atwo-dimensional measurement for the distance to the targeted portion ofthe document 102 that is acquired by the CCD camera 110, and transmitsthe distance information, via the controller 113, to the synthesizationcontroller 116 (ST101). The synthesization controller 116 analyzes theshape of the targeted portion of the document 102, based on the distanceinformation obtained by the distance measurement unit 111 (ST102), andperforms a perspective transformation for the preview image 119 that isread (ST103). The magnification rate is then calculated for the obtainedplane preview image 120, and is stored in the image memory 115 (ST104).FIG. 10A is a diagram showing the plane preview image 120 obtained bythe perspective transformation. Following this, the synthesizationcontroller 116 extracts a feature of the plane preview image 120(ST105). During this process, as is shown in FIG. 10B, an image area 120a or a text area 120 b is identified.

The resolution (optical magnification rate) is changed by controllingthe zooming of the CCD camera 110 (ST106), and an image is acquired of aspecific portion (text area 120 b) of the document 102 that requires ahigh resolution. That is, while watching a monitor (not shown), the usermanipulates the input unit 142 and enters the range for reading thespecific portion of the document 102. The CPU of the computer 104 thenemploys the information provided by the input unit 142 to transmit thecontrol signal for the CCD camera 110 and the scanner 112 to thecontroller 113 of the image reader 111 via the RS232C cable 103B. Basedon the control signal received from the computer 104, the controller 113controls the zooming and focusing functions of the CCD camera 110 andthe scanner 112 while the specific portion of the document 102 is read.The CCD camera 10 acquires, at a high resolution, the image of thespecific portion of the document 102, and transmits the pickup signalfor the obtained image segment 121 to the signal processor 114 (ST107).The signal processor 114 then performs signal processing, such as anamplification process and various correction processes, for the pickupsignal received from the CCD camera 110, and stores the obtained imagesignal in the image memory 115. At the same time as the CCD camera 110begins to acquire the image, the distance measurement unit 111 obtains atwo-dimensional measurement for the distance to the specific portion ofthe document 102 that is acquired by the CCD camera 110, and transmitsthe distance information, via the controller 113, to the synthesizationcontroller 116. Based on the distance information obtained by thedistance measurement unit 111 (ST108), the synthesization controller 116analyzes the shape of the specific portion of the document 102 andperforms a perspective transformation for the image 121 that is read(ST109). Thereafter, the magnification rate is calculated for the planeimage segment 122 obtained by the perspective transformation (ST110).

Following this, the synthesization controller 116 reduces the size ofthe plane image segment 122 obtained by a perspective transformationperformed at the same optical magnification rate as that of the planepreview image 120, i.e., at na/np, to obtain the plane image segment 123(ST111), and steps ST106 to ST111 are repeated until the reading of theimage segment 121 is completed. FIGS. 11A and 11B are diagrams showingtwo adjacent plane image segments 123 a and 123 b. When the reading ofall the image segments has been completed, distortion correction isperformed (ST112). As is shown in FIG. 1C, the plane image segments 123a and 123 b are synthesized, and as is shown in FIG. 12A, the obtainedplane image segment 123 c and the plane preview image 120 aresuperimposed to form a single complete image, which thereafter is storedin the image memory 115 (ST113). With this, the image reading iscompleted, and the complete image stored in the image memory 115 istransmitted to the computer 104, across the image signal line 113A, bythe controller 113, and is displayed on the display unit 141. FIG. 12Bis an enlarged diagram showing the portion obtained by synthesization.As is shown in FIG. 12B, the text area 120 b is read at a highresolution and clear characters are presented.

According to the above fourth embodiment, only a required portion of thedocument is read at a high resolution to obtain the image segment and ata low resolution to obtain the preview image, and the image segment andthe previous image are superimposed. Thus, the number of required imagesegments can be reduced and the time needed for synthesization can beshortened.

Further, based on the distance information, the image that is picked upis transformed into the plane preview image and the plane image segment.Thus, even an image of an area near the bound portion of an opened bookor an image of a portion of the curved face of a can be accurately read.

Fifth Embodiment

FIG. 14 is a diagram showing an image reader according to a fifthembodiment. In the fifth embodiment, the scanner 112 in the firstembodiment is not employed, and a detachable memory card 117, such as aflash memory or a RAM card, is mounted in a main body 101A to provide aportable image reader.

The processing for the fifth embodiment will now be described. First, auser sets a resolution using a zooming function, and scans the overalldocument 102 and a specific area of the document 2 using a hand-heldimage reader. At this time, together with the images, the distanceinformation is also obtained. As in the fourth embodiment, the overallimage and the image of the specific area are synthesized to form onecomplete image, and the complete image is read from the image memory 115and written to the memory card 117. The user loads the memory card 117into a driver 140 a of a computer 104, whereat the complete image isread, and thereafter the image is displayed on a display unit 141.

According to the fifth embodiment, since the scanner 112 is notincluded, a compact and light image reader that is suitable fortransportation by hand can be constructed, and the synthesization ofplane images can be performed by the computer 104, instead of the imagereader 111. In the fourth embodiment, since a high resolution image of aspecific area can be acquired by changing the optical magnificationrate, and in the fifth embodiment, since the image reader is portable, auser can hold the image reader while approaching a specific portion ofthe document 102, and an image of a specific portion can be acquired ata shorter distance.

Sixth Embodiment

FIG. 15 is a diagram showing an image reader according to a sixthembodiment. In the sixth embodiment, all the images and distanceinformation are written on a memory card 117, and a computer 104thereafter synthesizes images. According to this embodiment, a morecompact and lighter image reader can be constructed that is moresuitable for transporting by hand.

A text area may be acquired at a resolution that is consonant with thefont size. Further, three or more resolutions may be employed, dependingon the object.

The magnification rate employed for an image may be calculated based onthe zooming function of a CCD camera.

Furthermore, to synthesize a preview image at a low resolution and animage segment at a high resolution, the image segments may behierarchically positioned on the preview image, and an image segment maybe hieratically positioned on another image segment. Therefore, when animage segment is to be moved and positioned as a moving picture on apreview image, image processing can be facilitated.

As is described above, according to the image reader of this invention,perspective transformation is performed for multiple images that areacquired to prepare plane images, and the sizes of the plane images arealtered so that they correspond. Thus, for the synthesization of planeimages, even when an object is distorted, reading of an image of theobject can be performed accurately and quickly.

Further, since multiple images are acquired using a hand-held imagereader, and the distances to multiple target portions are calculated, acompact and light image reader can be provided.

1. An image reader comprising: an image pickup unit for imaging anobject at a predetermined resolution to obtain a first image, the imagepickup unit for imaging a specific portion of the object at a higherresolution than the predetermined resolution to obtain a second image;and a processing unit for reducing the size of the second image toobtain a reduced second image and superimposing the reduced second imageon the first image.
 2. An image reader comprising: an image pickup unitfor imaging a plurality of multiple adjacent target portions atdifferent resolutions from each other to obtain a plurality of multipleimages each having the different resolutions; and a processing unit forresizing the plurality of images in accordance with the differentresolutions to obtain a plurality of resized images, the processing unitfor synthesizing the plurality of resized images to obtain a singleimage.
 3. A method of reading an image, the method comprising: imagingan object at a predetermined resolution to obtain a first image; imaginga specific portion of the object at a higher resolution than thepredetermined resolution to obtain a second image; reducing the size ofthe second image to obtain a reduced second image; and superimposing thereduced second image on the first image.
 4. A method of reading animage, the method comprising: imaging a plurality of multiple adjacenttarget portions at different resolutions from each other to obtain aplurality of multiple images each having the different resolutions;resizing the plurality of images in accordance with the differentresolutions to obtain a plurality of resized images; and synthesizingthe plurality of resized images to obtain a single image.
 5. The imagereader according to claim 1, wherein the specific portion of the objectis determined based on the first image.
 6. The method according to claim3, further comprising determining the specific portion of the objectbased on the first image.